Em I crazy for swapping out my Mercruise 350 260hp?

knightowl

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Got a 79 Cruiser 350260hp small block v8.. Its a few years old but thinking about swapping out for a couple 225hp outboards.. sick of every year maintenance. takes a lot of room inside the boat, its alpha drive and I got a big 26ft boat with cab and bathroom inside that should have a big block diesel in this thing instead. what do you guys think? Not possible? outta my mind ? better off with diesel or better off on giving this small block more juice with these dumb log coolers?
 

tpenfield

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Re: Em I crazy for swapping out my Mercruise 350 260hp?

Do twin outboards ever need maintenance? Is an I/O to outboard conversion easy?

Definitely sounds like a 26 foot cruiser is under powered with just a 350. A lot would depend on your skills and money supply if you are going to D-I-Y. Also how would that compare to just buying a boat with outboards . . .
 

chimmike

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Re: Em I crazy for swapping out my Mercruise 350 260hp?

Seems to me converting transom to allow for dual outboards would be a lot of work. Then, dual outboards are pricey by themselves. You may be better off converting to a diesel like you're thinking and upgrading the outdrive?
 

Lou C

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Re: Em I crazy for swapping out my Mercruise 350 260hp?

If you are sick of I/O maintenance and aren't we ALL, LOL, then sell it and get a boat (smaller) with a single outboard. 2 outboards, or 1 diesel and the cost of conversion, is sky high expensive. Does not make sense, any way you look at it, except to be able to say "I did it"....
 

whatsagm

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Re: Em I crazy for swapping out my Mercruise 350 260hp?

If you dont like the up keep on an inboard wait till you get an outboard. I got rid of my outboards nothing but trouble and bought a boat with an inboard. Change oil once a year and thats all.
 

agallant80

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Re: Em I crazy for swapping out my Mercruise 350 260hp?

If you dont like the up keep on an inboard wait till you get an outboard. I got rid of my outboards nothing but trouble and bought a boat with an inboard. Change oil once a year and thats all.

Can you give more info? Why do you not like the inboard more then the outboard?
 

White Boat

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Re: Em I crazy for swapping out my Mercruise 350 260hp?

I think you answered your own question right away, go with a diesel. Less maintenance, lower fuel costs, and is less of a problem to do the conversion work. If its room you want get a bigger boat. Outboards will be more of a headache in the end run.
 

Fleetwin

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Re: Em I crazy for swapping out my Mercruise 350 260hp?

Look at some numbers.

Two 150-250 HP outboards are going to set you back at least $20 Grand. Not including brackets, installation, etc. Probably another $10 Grand.

A single diesel is going to be a LOT more and you're going to need a BIG one to match the 260 performance. HP is HP, torque is torque. A diesel conversion is probably $30 Grand-Plus.

You can probably get yourself another 100 plus HP with a complete stern drive set up and a Bravo III or Volvo Duo Prop for around $20 Grand. Plus the conversion would be MUCH easier.
 

White Boat

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Re: Em I crazy for swapping out my Mercruise 350 260hp?

Mitsubishi Marine Diesel Engines in Excellent Condition
Fully Serviced, Compression at Factory

6D16 T 225 hp at 2800 rpm
"0" Hours on Valve Grind $5500.00
Can be test run before purchase



EDIT
Please do not post phone numbers.
If you want the phone number, please just send a PM to White Boat.
Don S
 
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knightowl

Petty Officer 2nd Class
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Sep 20, 2008
Messages
111
Re: Em I crazy for swapping out my Mercruise 350 260hp?

Mitsubishi Marine Diesel Engines in Excellent Condition
Fully Serviced, Compression at Factory

6D16 T 225 hp at 2800 rpm
"0" Hours on Valve Grind $5500.00
Can be test run before purchase



EDIT
Please do not post phone numbers.
If you want the phone number, please just send a PM to White Boat.
Don S

How much bigger is the engine its self (tape measurement over size) then the 350 260hp Merc? As you can tell from the pictures, I don't have very much room in the engine compartment. I was thinking out loud when I posted I wanted outboard engines on this thing, I know it would take a lot of money and a lot of hours to convert. Im now leaning more towards dropping a new model 454 in there or a 502 with a bravo or Alpha 2 out drive to handle the more horse power.... The problem is in engine space ;( ......... The big question is do you think I will have room for a 454 or 502?


This is the 350 260hp pushing couple years ago or so. ( CLICK ON IMAGE TO PLAY VIDEO )



As you can see I am limited on room.



 
Last edited:

TilliamWe

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Re: Em I crazy for swapping out my Mercruise 350 260hp?

Big Block Chevy is not that much wider than a SBC. Forward clearance could be a bit of an issue, though.
 

Scott Danforth

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Re: Em I crazy for swapping out my Mercruise 350 260hp?

I would pull the motor, spend $2k to turn it into a 383 with center manifolds and go boating with a whole bunch more power.

or for about $500 (cam and gaskets) add about 30hp. the log manifolds are a bit restrictive as well compared to center riser manifolds.
 

knightowl

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Re: Em I crazy for swapping out my Mercruise 350 260hp?

Yes the center risers are my number 1 priority right now, any changes I make I will make sure I get the center risers... I CANNOT STAND the dumb log manifolds. They get so stinking hot and I wouldn't be surprised if my brand new rings on the pistons have over heated a bit already and I lost some compression... (going to go test it now)

As for the the 383, how do I convert to that? Boring the cylinders by 10 or 20? 30hp doesn't seem like it would do much difference on a big boat like that, just make the engine run hotter with same results. If we talking 70-100hp then yeah, I would feel it in my throttle then.
 

knightowl

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Re: Em I crazy for swapping out my Mercruise 350 260hp?

...another note, I herd the 454 and the 496 is only 2" longer and 3" wider, is that true?
 

Bondo

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Re: Em I crazy for swapping out my Mercruise 350 260hp?

...another note, I herd the 454 and the 496 is only 2" longer and 3" wider, is that true?

Ayuh,... 'bout that much,.... you've got plenty of room,...

The Alpha, Gen.IIs aren't any better than an Alpha 1, horsepower wise,...

You'll need a Bravo,...
 

Scott Danforth

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Re: Em I crazy for swapping out my Mercruise 350 260hp?

a 383 can be built to put out over 500 in a boat, however 400hp will be good reliable hp. that is different crank and rods.

you would also benefit from vortec heads, however thats another issue.

a simple cam change will get you 30hp, which would be enough to feel it a bit.

you mentioned running hotter. if your running hot now, find the issue.


highly recommend a Bravo if you go big block.
 

TilliamWe

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Re: Em I crazy for swapping out my Mercruise 350 260hp?

As for the the 383, how do I convert to that?...

A 350 has a 4" bore and a 3.48" stroke. A 383 has a 4.03" bore and a 3.75" stroke. So you would need to bore the engine .030 and install a 3.75" stroke crankshaft.

As stated above Vortec heads will WAKE up a 350, but it requires a different intake manifold as well.
 

Scott Danforth

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Re: Em I crazy for swapping out my Mercruise 350 260hp?

TilliamWe, you are correct, however no one knows what a 377 is. the extra 5 cubes is from the .030 over bore
 

oldseattle

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Jan 6, 2015
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I have a pair of those Mitsubishi diesels (they're actually called Chrysler CM-655s) in my old 42' Chris Craft. I took out a pair of small block Chevrolet gas engines and replaced them with the Chrysler-Mitsubishi diesels. The CM-655 is a slower turning, heavier, longer, taller and much less powerful engine. It would never fit in your space and even if it did you would be unhappy with the performance. If you're dead set on diesel, buy either a Volvo or a Yanmar. They're essentially drop in replacement for gas V-8s. That being said, the CM-655 is great for a slower, heavier, non planing boat, just not yours. Any questions, let me know.
 
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